Loud-speaker



Jan. 27, 1931. A1 THQMAS 1,790,120

LOUD SPEAKER Filed May 24 1926 2 Sheets-Sheet 1 v Jan. 27, 1931. A A THAS 1,790,120

LOUD SPEAKER I Fild May 24 192 2 Sheets-Sheet 2 70 INVENTOR' PatentedJan. 27, 1931 UNITED STATES ADOLPH A. THOMAS, OF NEW YORK, N. Y.

LOUD-SPEAKER Application filed Kay 24,

My invention relates to electric sound-reproducing devices and itsobject is to provide a loudspeaker in which a small diaphra amplifyingthrough a horn is com- 6 bine with a large cone-shaped. diaphragm.

This produces an instrument capable of reproducing the upper and lowerregisters of sound frequencies with equal fidelity.

In the loudspeaker of my invention, there is a hollow base on which ismounted a horn for amplifying the vibrations of a small diaphragm.Within the base is supported a large diaphragm in horizontal osition.This diaphragm is conveniently but not necessarily) of the well-knowncone type.

Both diaphragms are simultaneously operated by suitable electromagneticmechanism. The vibrations of the large diaphragm pass out of the hollowbase through openings into 2 the free air. The bottom of the base may beclosed by a sounding boardto accentuate or reinforce the air vibrationsproduced by the large diaphragm. Thus, in the" operation of theinstrument, the higher tones issue'out of the horn, while the lowertones come from the base chamber.

In a preferred embodiment of my invention, the small upper diaphra iscontrolled by a coil or coils which ten to accentuate the higherfrequencies, while the large diaphragm in the base is controlled by oneor more coils so connected in circuit as to cause the lower frequenciesto predominate. In this way, the operative control of each dia-,

phragm is independent of the other. In order to regulate the action ofthe controlling coils, I connect a variable choke coil across the coilsof the small diaphragm and a variable condenser across the coils of thelarge diaphragm. These variable devices are mounted on the base so as tobe adjustable by simply turning a knob or the like. This enables theoperator readily to vary the quality of reproduction to suit his ownmusical taste.

In addition to means forcontrolling the quality of reproduction, I mayalso provide my new loudspeaker with means for control- I ling thevolume or loudness of the reproduced sound. At the present time I preferan ad- 1926. Serial No. 111,149.

justable magnetic shunt for regulating the efi'ective strength of themagnet structure.

The accompanying drawings illustrate several embodiments of myinvention, wherein- Fi 1 re resents a vertical cross-section of 5 oneorm o my inproved loudspeaker, a portion of the base and the largediaphragm being broken away for lack of space;

Fig. 2 is a plan view on the broken line 2-2 of Fig.1; I 50 Fig. 3 showsan enlarged detail view of the adjustable mounting of the armature onthe cone diaphragm;

Fig. 4 is a view similar to Fig. 1, but at ri ht-angles thereto; o5

ig. 5 is a detached view in plan to show the connections for adjustingthe core of the choke coil which is shunted across the coils thatoperate the upper diaphragm;

Fig. 6 illustrates in cross-section a modified construction wherein thecone diaphragm is mounted with its apex pointing'downwardly;

Fig. 7 is a fragmentary detail view showing a knob for controlling thevolume or loudness of the cone diaphragm;

Fig. 8 shows a parallel arrangement of the magnets for the twodiaphragms, making in efiect a single magnet controlled by one mag- Lnetic shunt; and I Fig. 9 indicates diagrammatically suit- 30 ablecircuit connections for the controlling coils.

Before beginning a detailed description of the drawings, I want to makeit plain that the various figures are not intended to reps5 resentaccurate shop drawings. On the contrary, I have purposely shown variousparts aluminum, whichis light, strong and nonmagnetic. The particularshape and dimensions of the base will naturally vary in accordance withthe size and mounting of the cone diaphragm, as will presently becomeclear. Ordinarily, base B will be circular in design; for example, itmay be a flat or corrugated disk, and may be of metal, wood and othersuitable acoustic materials. The diaphragm C is rigidly clamped at itsperiphery to. an annular flange or shoulder 10 at the bottom of the baseby means of a ring 11 secured to flange 10 by screws 12. In thisinstance, the clamping ring 11 is part of a cone-shaped disk 13 arrangedparallel with the diaphragm and forming a bottom closure for the basechamber 14. Disk 13 may be made of resonant material to act as asounding board for reinforcing the vibrations of diaphragm C. The base Bis provided with legs 15 to hold the disk or board 13 clear of thesupport on which the instrument stands and allow the vibrations of thedisk to escape into the free air all around. The vibrations of diaphragm0 pass freely out of the base chamber 14 through openings 16 ar rangedradially all around the conical wall of the base. In Fig. 1 theseopenings have been purposely omitted, so as not to obscure certain partswithin the base chamber.

On base B is mounted a cylindrical casing 17 having a bottom plate 18and an outer flange 19. These parts are preferably cast or molded as aunit out of suitable nonmagnetic material, such as aluminum, bakelite,etc. The flange 19 rests on an annular seat 20 at the top of base B, andscrews 21 secure the casing 17 rigidly to the base. The seat 20 ispreferably depressed to provide a circular recess 22 into which flange19 fits snugly to afford additional holding means for the casing and atthe same time facilitate assembling of the parts. In the upper end ofcasing 17 is mounted a diaphragm D. A cover plate 23, removably securedin position by screws 24, holds the diaphragm D firmly clamped between apair of gaskets or washers 25 of rubber, felt or like material. Acircular ledge 26 formed within the casing acts as a support for thediaphragm. The cover plate 23 is provided with a tubular extension 27for receiving the neck of a horn 28 through which the vibrations ofdiaphragm D are amplified. This diaphragm may be magnetic, or it may beof non-magnetic material, such as aluminum, German silver, wood, etc. Ifnon-magnetic, diaphragm D carries an armature 29, preferably in the formof a small thin iron disk attached centrally to the underside of thediaphragm.

The electromagnetic mechanism for operating the diaphragms C and Dcomprises, in

best shown in Figs. 2 and 8. As the magnets are flat, they can bestamped out of steel plates. The circular form of the magnets provides amaximumlength of magnetic path in the cylindrical casingl'l'. To thepolar limbs of each magnet are fastened pole pieces 32, which project atright angles to the body of the magnet. The pole pieces of the uppermagnet M project upwardly toward the small diaphra m D, andthose of thelower magnet M project downwardly toward the large diaphragm C. Bymaking the pole pieces 32 L-shaped, it is possible to secure them firmlyto-the polar limbs 31 (as by screws 33) over a large contact area. InFigs. 1 and l, the two magnets are so mounted'that their polar limbsextend at right angles to each other, for a purpose that will later beexplained.

Onthe pole pieces of magnet M are mounted coils K, and on the polepieces of magnet M are mounted coils K. Since each pair of coils isconnected in series, these four coils are in effect but two coils, andso I shall refer to them as coil K and coil K, respectively.

As seen in Figs. 1 and 4, the pole pieces 32 of magnet M terminate closeto armature 29 of diaphragm D, or close to the diaphragm itself if thelatter is of magnetic material. The pole pieces of magnet M extendtoward the armature 34 of diaphragm C. This armature is preferably inthe form of a small disk adj ustably secured to the diaphragm to permitregulation of the normal airgap between the armature and the polepieces. The two armatures should be large enoughto span the pole piecesfully, not only transversely ,buiTalso in the direction of their length.The enlarged view of Fig. 3 illustrates a practical way of mounting thearmature 34 for axial adjustment. The diaphragm C carries at the centera bushing 35 which is screw-threaded inside and outside. The bushing isfixed in position by means of a pair of cone-shaped disks 36, whichengage the diaphragm on opposite sides. The upper disk 36 bears a ainst(or is made integral with) a collar 3% on bushing 35. A nut 38 screwedon the bushing holds the disks 36, and thereby the bushing itself,rigidly clamped to the diaphragm. A screw-threaded rod or bolt 39,secured to the center of armature 34, passes through bushing 35 in whichit is axially adjustable, as by means of a screw-driver or likeimplement inserted into the head 40. The disk or sounding board 13 isprovided with a small central opening 41 to permit access tothe armaturebolt 39 without dismantling any portion of the in- Figs. 1 and 5. Theiron core 50 is axially adstrument. A coil spring 42, or equivalentjusted with respect to the coil by a stiff cam means. employed to holdthe bolt 39 in ad wire or rod 51 secured to a shaft 52 which is justedposition without the possibility of ratturned in either direction byknob 48. The tli'ng during the vibrationsof the diaphragm. outer end ofcore 50 has'an eye 53 through The controlling coils K and K are conwhichpasses the cam wire 51. In Figs. 1 nected in parallel to the leads l3,wh'ch may and 5, the core 50 is almost entirely withterminate in a plug4H, as diagrammatically indicated in Fig. 9. The ends of the upper coilor coils K pass into the base chamber 14 througha small hole 45 in thebottom plate 18. The leads 43 pass through a conveniently locatedopening (not shown) in base B. thcr explanation, that current impulsespassquency cause simultaneous vibration of diaphragms C and D toreproduce the sound waves of which the variable current impulses are (asit were) an electrical representation. Since the tendency of the largediaphragm C is to accentuate the lower register on the musical scale,while diaphragm D tends to accentuate the upper register. it ispossible, by correctly designing these diaphragms, to reproduce thewhole range of audio-freque'ncy tones with practically uniformintensity. It will he noticed that the bottom plate 18..which preferablynon-resonant, acoustically separates the interior of casing 17 from thebase chamber 14. so that the vibrations of either diaphragm do notdisturb the vibrations of the other.

\Yhile the diaphragms D andC will naturally respond best to the higherand lower bands of frequencies. even though all frequencies pass throughcoils K and K. I prei'er so to modify the action of the controllingcoils that the higher frequencies pass most easily through coil K ofdiaphragm D and the lower frequencies pass most easily through coil K ofdiaphragm C. To this end. a choke coil 46 is connected across coil K.and a condenser 47 is connected across coil K. The choke coil tends toabsorb low-frequency in pu'lses. allowing high frequencies to traversethe coil K. The action of the condenser is the reverse, in that itallows low frequencies to pass through coil K. It'is clear that byregulating the self-induction value of choke coil 46 andthe capacity ofcondenser 47, the operation of coils K and K is correspondinglycontrolled. That is to say. it is ble in this way to select the range offrequencies that shall pass through (or predominate in) coil K and coilK. In 1. the regulating devices 46 and 47 aremounted on base ll in suchpositionthat a turnable knob 48 varies the self-inductance ot' chokecoil 46. while a knob 4-9 varies the capacity of condenser 47. It is notnecessary to show any structural details of a variable condenser.because there are many familiar makes of that type of condenser on themarket. A simple way of regulating choke coil $6 is shown in It will beunderstood without furmg through coils K and K at audio fre- 4 poss1-drawn from coil 46. so that the choking action of the coil is at aminimum. As the cam 51 is turned clockwise (as viewed in Fig. the coreis moved into the coil 46 to increase its choking cfi'ect. \Vhen the cam51 is in the position indicated by dotted lines 51, the core 50 isentirely within the coil. so that now its self-imluctance is a maximum.the extreme in and out positioiis of the inner core. any intermediateposition may be obtained. The iron core remains in adjusted position.since. the connection between the core and cam 51 does not permit thecore to be suckedinto thecoil by the magnetic action of the latter. Astrap 54. attached at its ends to the slanting wall of base B. holds thechoke coil firmly in position. If desired. strap 51 may be provided withan arm or extension to guide the core in its axial movements.

.ltwill be understood from the preceding paragraph that the operator canreadily control the frequency-selecting action of coil K for the horndiaphragm D and of coil K for the base diaphragm C by simply turning theknobs 48 and 49. I have thus provided simple means for controlling thequality of rcprmluction of the instrument for each diaphragm. This isnot intended as a regulation of mere volume or loudness. for whichseparateprovisions are made, as now to be described.

Referring to Figs. 1 and 2. there is a, mag netic block 56 (preferablyof soft iron) arranged to slide over the bottom plate 18't0- ward andaway from the pole limbs 31 of magnet M. The plate 18 has a lug 57 witha screw-threaded hole through which passes a screw-threaded rod 58 ofnon-magnetic material. The inner end of rod 58 is rotatably connected tothe magnetic block 56. as indicated at 59. The other end of the rodextends outside the casing 17 where it is provided with a knob 60 foreasy manipulation. WVhen the knob 6Q is turned in one direction (say,clockwise). the rod 58 pushes the magnetic block 55 away from the-polepieces toward the neutral portion of the magnet. In Figs. 1 and 2, theblock 56 is practically without effect on the normal field flux acrossthe pole pieces. \Vhen the knob is turned the other way, the-magneticblock is drawn toward the polar limbs of the magnet. The closer itapproaches the polar limbs 31, the more flux does it short-circuit andthe weaker become the pole pieces 32 that provide the effective flux forarmature 29 of diaphragm D. In other words. the ma netic block 56 actsas a shunt for the field flux and by its Between "obtained.

In exactly the same way is the loudness of the large diaphragm Ccontrolled by an adjustable magnetic shunt 56 (see Fig. 4), whicharranged to slide in a direction at right angles to that of block 56. sothat neither shunt block shall affect the other magnet. For this purposethe magnets M and are arranged at right angles to each other, aspreviously explained. The block 56' is shifted back and forth by meansof a non-magnetic rack-bar (i1 slidably supported in a lug (52 dependingfrom plate 15.. The teeth of rack-bar ()1 are in mesh with a pinion (33fixed at the inner end of a rotary stud 64 mounted on base li. as shownin F g. 4. A knob (35, or other finger piece. permits 'ready adjustmentof magnetic block 56.

\Vhat has been said about the position of magnetic shunt 56 controllingthe ett'eetive strength of magnet. M, is applicable to magnetic block56' in similarly controlling the operative strength of magnet M and theloudness of diaphragm C. in Fig. l. the shunt block 56 is shown in loudposition. while in Fig. 6 it is shown in soft posi tion. In fact, whenthe magnetic shunt 56 or 56 is in contact with the polar limbs of theassociated magnet. there is practically no flux passing through the polepieces 32. so that the adjacent diaphragm is rendered inoperative. Thisatl'ords an easy way to cut out either diaphragm when desired.

The only ditlerence between Fig. (3 and the other figures is thatdiaphragm C is supported in base l)" with its apex pointing down. inthis instance. the cone diaphragm is clamped between an inner ring (it;and an outer ring (ii. The inner ring has a series of lugs tie throughwhich pass screws {39 to secure the diaphragm against the underside ofthe base. The bottom closure or sounding hoard i2, is fastened by screwsT0 to interior lugs T1 on the base. The lugs T1. be ng spaced at.intervals. do not prevent the insertion of diaphragm held in clampings(it; and 67. because the ring or; can be so positioned that the lugs (38pass by the lugs Tl. The vibrations of diaphragm pass into the free airthrough openings 72 in the base. 'hat has been previously said about theoperation and control of the diaphragms in l igs. k5. is tallyapplicable to Fig. t3. without the need r petition.

ii ill e seen from the preceding oescrip- ,tion that I have provided acombined horn and cone loudspeaker of compact construction and neatappearance. The large diaphragm is concealed in the base, and thereforeadds little to the dimensions of an ordinary horn speaker. except that abroader base is needed, depending upon the diameter of the conediaphragm. These diaphragms run all the way from about six inches toeighteen inches or more. A wide base is not objectionable, since it canbe made ornamental in color and design, and furthermore it addsstability to the instrument. The 'ease with which the quality and volumeof reproduction can be controlled increases the usefulness of thisdouble loudspeaker. It is not necessary, however. that all thecontrolling connections previously described shall be embodied in thesame device.

Various changes and modifications may be resorted to in practising myinvention. For instance. instead of arranging the magnets M and M atright angles to each other and having a separately controlled magneticshunt for each. I may arrange the magnets in parallel relation with asingle shunt; for both. as indicated in Fig. 8. The supporting plate 18for the magnets may be separate from casing 17 and formed as'an integralpart of the top of the base. My invention is not limited to any specificconstruction or mounting of electromagnetic mechanism for operating thetwo diaphragms. and what I have shown in the drawings is to be regardedas illustrative and not restrictive. The basic idea of operativelymounting a large hornless diaphragm horizontally in the base of aloudspeaker having also a small diaphragm that amplifies through a horn.may be embodied in other ways than herein set forth. It is evident thatcertain features of my invention may be used without other features.

Thus, in a simplified form of loudspeaker. theff cone portion may beconstructed without the horn portion.

What I claim as my invention is:

l. loudspeaker having a base constructed to provide an open chamber. ahorn supported on said base. a diaphragm acoustically connected withsaid born, a large direct-acting diaphragm operatively mounted in saidopen base chamber and acoustically disconnected from said horn. wherebysaid large diaphragm iscdmpletely housed in said base and yet freelyopen to the outer air. and electromagnetic means for simultaneouslyoperating both diaphragms.

2. A loudspeaker comprising a hollow base freely open to the outer air.a small diaphragm mounted in the upper part of said base. a hornsupported on said. base and zu-oustically connected with said smalldiaphragm. a large diaphragm mounted horizontally in said base belowsaid small dia phragm and completely housed in said base,

the vibrations of said large diaphragm passing through the open baseinto the free air, means in said base for preventing the vibrations ofthe large diaphragm passing through the horn, and electromagnetic meansin said base for simultaneously operating said diaphragms.

3. A loudspeaker having a base provided with a-small upper' chamber anda large lower chamber, a partition between said chambers, said lowerchamber having lateral sound openings, a horn extending from said upperchamber. a small diaphragm in said upper chamber. a large diaphragm insaid lower chamber, said diaphragms being arranged substantially inhorizontal position, and electromagnetic mechanism mounted on saidpartition for actuating said diaphragms, the vibrations of the largediaphragm passing through said lateral openings into the outer air.

4. A combined horn and cone loudspeaker having a hollow supporting basein which a direct-acting cone diaphragm is operatively mounted inhorizontal position, said base completely enclosing said con diaphragmand having openings for the emission of sound from said diaphragm, ahorn supported on said base, a diaphragm acoustically connected withsaid horn, and electromagnetic mechanism for operating said diaphragms.

5. In a loudspeaker,'a hollow supporting structure provided with twochambers, a small diaphragm in one'chamber,. a large diaphragm in theother. chamber, said hollow supporting structure enclosing bothdiaphragms, a sound-amplifying,passage leading from said first chamber,electromagnetic mechanism within said structure for operating saiddiaphragms. said structure having openings through which the vibrationsof the large diaphragm pass into the outer air, and a partition. in saidstructure for acoustically separating the chamber of the large diaphragmfrom said amplifying passage.

6. In a loudspeaker, an. upright hollow base having a sound passage ontop for communicating with a horn, "a horizontal diaphragm mounted insaid base adjacent said passage for sending sound vibrationstherethrough, a second diaphragm enclosed in said hollow base andsupported in horizontal position below said first diaphragm, a partitionarranged in said base to acoustically separate the second diaphragm fromsaid sound passage, and electromagnetic mechanism mounted on saidpartition for operating said diaphragms, said base having openings forthe escape of sound waves from said second diaphragm.

7. A loudspeaker comprising a hollow non magnetic casing provided with abase and having sound openings above said base, a direct-acting conediaphragm supported horizontally in said casing above said base andfreely open to the outer airthrough said sound openings, said conediaphragm being completely housed in said hollow casing, anelectromagnetic driving unit mounted in said casing above saiddiaphragm, and means whereby said unit is insertable into and removablefrom said casing without disturbing the diaphragm which is supportedinde p'endently of said unit.

8.- In a loudspeaker, a hollow base provided with lateral soundopenings, a cone diaphragm enclosed in said hollow base and supportedhorizontally therein with its apex pointing upwardly, an armature fixedto the center-of said diaphragm, and electromagnetic mechanism mountedin said base above said diaphragm for operating the same throughthemedium of said armature, said diaphragm being supported independently ofsaid mechanism.

9. In a. loudspeaker, a cone diaphragm provided at the center with aninternally threaded bushing extending axially of the diaphragm, meansfor rigidly holding said bushing in place, a screw mounted in saidbushing and wholly supported thereby, said screw projecting at one end'out of said bushmg, an armature fixed on said projecting end of'thescrew which is adjustable in said bushing, resilient means engaging saidscrew to hold the same firmly in adjusted position during the vibrationsof the diaphragm, and electromagnetic means in operative relation tosaid armature.

10. In a sound-reproducing device, a hollow base open for the passage ofsound, a direct-acting cone diaphragm enclosed in said hollow base andsupported horizontally therein, an electromagnetic unit in said base foroperating said diaphragm, and means whereby said diaphragm is supportedindependently of said unit.

11. In a loudspeaker, a hollow base provided with sound openings, a conediaphragm horizontally supported in said base with its apex pointingupwardly, a atone-shaped sounding board mounted in said base below saiddia hragm, said "board also forming a closure or the bottom of the base,and electromagnetic mechanism mounted in said base above said diaphragmfor operating the same.

12. In a loudspeaker, a pair of diaphragms having different acousticproperties, electromagnetic meohanism for simultaneously operating saiddiaphragms, and magnetic means adjustable independently of saidmechanism and said diaphragms for con trolling the operative flux ofsaid mechanism to regulate the volume of reproduction of each diaphragm,said means permitting either diaphragm tobe cut out of operation.

13. Ina loudspeaker, a magnet structure having two pairs of pole piecesextending in opposite directions, a small diaphragm mounted on one sideof said structure in operative relation to one pair of pole pieces, ahorn acoustically connected with said small diaphragm, a largedirect-acting diaphragm mounted on the other side of said structure inoperative relation to the other pair of pole pieces, a controlling coilon each pair of pole pieces, said coils being connected in parallel topermit independent operation" of said diaphragms, and means foracoustically disconnecting said large diaphragm from said horn.

14. In a loudspeaker, a magnet structure having two pairs of pole piecesextending in opposite directions, a small diaphragm mounted on one sideof said structure in operative relation to one pair of pole pieces, ahorn acoustically connected with said small diaphragm, a largedirect-acting diaphragm mounted on the other side of said structure inoperative relation to the other pair of pole pieces, a controlling coilon each pair of pole pieces, said coils being connected in parallel topermit independent operation of said diaphragms, means for acousticallydisconnecting said large diaphragm from said horn and manuallycontrollable means for varying the effective response of said coils todifierent bands of frequencies.

15. A combined horn and cone loudspeaker having electromagneticmechanism mounted between the two diaphragms for simultaneouslyoperating the same, and manually controllable means for regulating theloudness of the horn diaphragm and the cone diaphragm independently. ofeach other, said means permitting either diaphragm to be cut out ofoperation.

16. A loudspeaker comprising a hollow base having sound openings, a hornsupported on said base, a small diaphragm mounted in the upper part ofsaid base and acoustically connected with said horn, a large diaphragmsupported horizontally within said base, electromagnetic mechanism foroperating said diaphragms, said mechanism including a controlling coilfor each diaphragm, a variable. condenser and an adjustable choke coilmounted within said base, said condenser being connected across theoperatin coil of the large diaphragm and said cho e coil being connectedacross the operating coil of the small diaphragm and a pair of fingerpieces on the outside of said base for separately adjusting saidcondenser and said choke coil and thereby varying the effective responseof said operating coils to difierent bands of frequencies, whereby thequality of reproduction of either diaphragm may be varied as desired.

17 A loudspeaker comprising a hollow base member open at the top andhaving an annular seat around the top opening, a casing adapted to reston said seat, said base vmember being of considerably greater diameterthan said casing, means for securing said casing in position on saidbase member, said casing having a bottom plate: which closes the top ofsaid base member, a diaphragm mounted in said casing, a horn connectedto the upper end of said casing for amplifying the vibrations of saiddiaphragm, a large diaphragm supported horizontally in said hollow basemember, and electromagnetic mechanism secured to said bottom plate forsimultaneously operating said diaphragms independently of each other,said mechanism being arranged partly on the upper side of said plate andpartly on the underside thereof.

18. A loudspeaker comprising a hollow base provided with two chambersacoustically separated from each other, said chambers having soundopenings leading to the outer air, a diaphragm mounted in one of saidchambers, a second diaphragm mounted in the other chambers, said hollowbase completely enclosing both diaphragms, which have different naturalfrequencies to accentuate high and low tones, and electromagneticmechanism in said base for operating said diaphragms. 3

19. A combined horn and cone loudspeaker comprising a hollow base, ahorn mounted on said base, a horizontal partition in said base toprovide a small upper chamber and a large lower chamber, said chambers;being acoustically separated by said partition, said lower chamberhaving sound openings to the outer air, a small diaphragm arranged insaid upper chamber and acoustically connected with said horn, a largedirect-acting diaphragm in said lower chamber, said hollow basecompletely enclosing said diaphragms, and electric means in said basefor operating said diaphragms.

20. A combined horn and cone loudspeaker comprising a-hollow base, ahorn mounted on said base, a horizontal partition in said base toprovide a small upper chamber and a large lower chamber, said chambersbeing acoustically separated by said'partition, said lower chamberhaving sound openings to the outer air, a small diaphragm arranged insaid upper chamber and acoustically connected with said horn, a largedirect-acting diaphragm in said lower chamber, electric means in saidbase for operating said diaphragms, and a sounding board arrangedhorizontally 1n said lower chamber to amplify the vibrations of saiddirect-acting diaphragm.

21. A combined horn and cone loudspeaker having a hollow base in which acone diaphragm is completely housed and operatively mounted inhorizontal position, a horn rigidly supported on said base, a diaphragmacoustically connected with said horn, said cone diaphragm beingacoustically disconnected from said horn, electromagnetic mechanism insaid base for operating said diaphragms, and means in. said base forregulating the loudness of the two diaphragms independently of eachother.

22. A combined horn and cone loudspeaker having a hollow base in which acone diaphragm is operatively mounted in horizontal position, a hornrigidly supported on said base, a diaphragm acoustically connected withsaid horn, said cone diaphragm being acoustically disconnected from saidhorn, means in said base for independently regulating the loudness ofthe two diaphragms to obtain the best acoustic blending of the tones,and a pair of manually adjustable members outside said base forcontrolling said means independently for each diaphragm.

23. A loudspeaker having a plurality of diaphragms of different acousticproperties, electromagnetic mechanism for simultaneously operating saiddiaphragms, and mag netic means independent of said mechanism and saiddiaphragms for influencing said mechanism to simultaneously regulate thevolume of reproduction of all diaphragms. 24. In a loudspeaker, a pairof diaphragms having different acoustic properties, electromagneticmechanism for simultaneously operating said diaphragms, and magneticmeans adjustable independently of said mechanism and said diaphragms forcontrolling the operative fiux of said mechanism to regulate the volumeof reproduction of each diaphragm independently of the other.

25. An electric acoustic device comprising a hollow upright casing inwhich a cone 'diaphragm is supported in horizontal position, said casingbeing open for the passage of sound from said diaphragm into the outerair, electromagnetic mechanism in said casing for operating saiddiaphragm, and a resonance board mounted horizontally in said casing inoperative relation to said diaphragm, the vibratory surface of saiddiaphragm being freely exposed in said chamber awayfrom said mechanism.

26. An electric acoustic device comprising a hollow upright casing inwhich a cone diaphragm is supported in horizontal position. said casingbeing open for the passage of sound from said diaphragm into the outerair, electromagnetic mechanism in said casing for operating saiddiaphragm, and a cone-shaped board mounted in the casing opposite saiddiaphragm, the apices of said diaphragm and board extending toward eachother, whereby said diaphragm and board form a circular acoustic chamberwith outwardly diverging upper-and lower walls which deflect the soundthrough the open casing into the outer air.

27. In a loudspeaker, the combination of a hollow base enclosing a largedirect-acting diaphragm and having sound passages through which saiddiaphragm is freely open to the outer air, a sound-amplifying membermounted on said base and acoustically disconnected from said conediaphragm, a small diaphragm carried by said base and acousticallyconnected with said amplifying member, and electric mechanism foroperating said dia-phragms.

28. In a loudspeaker, the combination of a hollow base having an openingat the top and being provided with lateral sound passages, a largediaphragm enclosed in said hollow base and freely open to the outer airthrough said passages, a casing adapted to fit into said top opening ofthe base, means for securing said casing on said base, a small diaphragmmounted in said casing, a horn connected to said casing for amplifyingthe vibrations of said small diaphragm, and electric mechanism arrangedbetween said diaphragms for operating the same.

29. In a loudspeaker, the combination of i a hollow base having anopening at the top and being provided with lateral sound passages, alarge diaphragm enclosed in said hollow base and freely open to theouter air through said passages, a casing adapted to fit intosaid topopening of the base, means for securing said casing on said base, asmall diaphragm mounted in said casing,a horn connected to said casingfor amplifying the vibrations ofsaid small diaphragm, and electricmechanism carried by said casing for operating said diaphragms.

30. A combined horn and cone speaker comprising a direct-acting conediaphragm and a small diaphragm amplifying through a horn, means formounting said diaphragms in fixed spaced relation, electromagneticmechanism for simultaneously operating said diaphragms, and means forregulating the loudness of said diaphragms independently of each other,said regulating means permitting either diaphragm to be cut out ofoperation. V

31. A combined horn andcone speaker having electromagnetic mechanism forsimultaneously operating the cone diaphragm and the horn diaphragm,means for supporting said diaphragms in fixed spaced relation andmanually adjustable magnetic means associated with said mechanism forregulating the volume of reproduction separately for each diaphragm.

32. A loudspeaker having a circular hollow base sloping downwardly fromthe center toward the periphery, said base forming a chamber freely opento the outer air, a direct-acting cone diaphragm supported horizontallyin said base chamber with its apex pointing upwardly, andelectromagnetic mechanism carried by the base above said diaphragm foroperating the same.

33. A combined horn and cone speaker comprising a small diaphragm and acone diaphragm supported in concentric spaced relation, a hornacoustically connected withsaid small diaphragm, said cone diaphragmbeing acoustically disconnected from said horn and directly open to theouter air, and electromagnetic mechanism mounted between said diaphragmsfor actuating the same independently of each other.

34. A loudspeaker having a hollow casing which constitutes a supportingbase, a pair of diaphragms mounted in said casing, said diaphragmshaving ditferent acoustic prop erties, electromagnetic mechanism in saidcasing for simultaneously operating said diaphragms independently ofeach other, electric means in said casing for controlling the quality ofreproduction of each diaphragm independently of the other diaphragm,means associated with said mechanism for'regulating the volume of eachdiaphragm independently offthe other diaphragm, and a plurality ofhand-operable connections projecting from said casing for operating saidquality-controlling means and said volumecontrolling means independentlyfor each diaphragm.

35. As a unitary construction, a combined horn and cone speakercomprising a directacting cone diaphragm'and a small diaphragmamplifying through a horn, means for mounting said diaphragms inconcentric spaced relation, the small diaphragm being arranged above thecone diaphragm, means for acoustically separating said diaphragms, andelectromagnetic mechanism arranged between 'said diaphragms foroperating the same.

36. A combined horn and cone speaker comprisinga horn supported invertical position, a small diaphragm at the inner end of said horn, aloudspeaking cone diaphragm supported below said horn in substantiallyconcentric relation to said small diaphragm, said cone diaphragm beingacoustically dis: connected from the inner end of said horn and freelyopen to the outer air, and electromagnetic mechanism mounted betweensaid diaphragms for operating-the same.

37. A combined horn and cone speaker comprising a substantiallyconical'casing flaring outwardly toward the bottom, a cone diaphragm atthe lower end of said casing and freely exposed to the outer air, a hornmounted above said casing in substantially concentric relation to saidcone diaphragm, a small diaphragm communicating with the inner end ofsaid horn, said cone diaphragm being acoustically disconnected from saidhorn, and electromagnetic mechanism arranged between said diaphragms foroperating the same.

38; A combined horn and cone speaker comprising a substantially conicalcasing flaring outwardly toward the bottom, a cylindrical housingmounted on top of said casing and projecting above the same,'sa1dhousing containing a diaphragm and electromagnetic actuating meanstherefor, a horn mounted over said casing and connected at its inner endwith said diaphragm, a loudspeaking cone diaphragm at the flaring lowerend of said casing and freely exposed to the outer air, said twodiaphragms being'arranged in substantially concentric relation, and anelectromagnetic unit insaid casing below said housing for operating saidcone diaphragm, said cylindrical housing having a bottom wall or platewhich separates the two diaphragms acoustically from each other. 39. Ina loud speaker, a compound unit having parts for translating sound wavesof different tone qualities, one of the said parts having a metaldiaphragm, the other of the parts having an armature, a permanent magnetfor' producing a field of force in the metal diaphragm and in thearmature, and a megaphonic means for amplifying the sound produced bythe diaphragm and the armature.

40. In a loud speaker, a permanent magnet, two pole pieces operativelyconnected to each pole of the magnet, one pair of pole piecesterminating on one side of the magnet, the other pair of pole' piecesterminating toward the other side of the magnet, an armature adjustablypositioned in relation to one pair of pole pieces, an armature formingdiaphragm positioned in relation to the other pair of pole pieces,electromagnetic coils associated with the pole pieces adapted to varythe magnet influence of the pole pieces on the armature and on thediaphragm to cause the armature and the diaphragm to vibrate, and meansto amplify the vibration of the armature and the diaphragm into audiblesound waves.

41. In a loud speaker, a compound mag netic unit comprising a permanentmagnet, two pairs of pole pieces secured to the poles of the magnet andprotruding from opposite sides of the magnet, coils located on on thesaid pole pieces, a metal diaphragm located in operative relation to onepair of the pole pieces, an armature located in operative relation tothe other pair of pole pieces, a horn located in operative relation withrespect to the metal diaphragm and a flexible diaphragm mechanicallyconnected to the armature.

42. A cone loudspeaker comprising a horizontal base, a cone diaphragmmounted horizontally on said base with its apex pointing upward, saiddiaphragm being directly open to the outer air, a frame above said baseand diaphragm, and an electromagnetic driving unit for said diaphragmsecured to said frame. V

43. In loud speaker mechanism, the combination of a substantiallyhorizontal supporting frame comprising an upper member and a lower basemember, a: cone diaphragm mounted horizontally between said members withits apex pointing upward, said diaphragm being directly open to theouter air, and an electromagnetic device attached to said upper memberfor operating said diaphragm.

44. A loudspeaker comprising a top member and a. base member arranged toform a housing open' tothe outer air, a cone diaphragm supportedhorizontally in said housmg, and electromagnetic mechanism dependingfrom said top member for operating said diaphragm.

45. 'In loudspeaker mechanism, the combination of a substantiallyhorizontal supporting frame comprising an'upper member and 5 a lowerbase member, a cone diaphragm mounted horizontally between said membersand directly open to the outer air, and an electromagnetic deviceattached to said upper member for operatin said dia hragm.

' 46. In a loudspea er, a hollow structure provided with sound openings,a cone diaphragm horizontally supported in said structure, a soundingboard mounted in said structure below said diaphragm, said board alsoforming a closure for the bottom of said structure, and electromagneticmechanism mounted in said structure above said diaphragm for operatinthe same.

47. A loudspeaker avin at least tw' -!iaphragms mounted in spacerelation, e trio mechanism mounted between said diaphragms forsimultaneously 0 crating the same, and. manually controllab e means forregulating the loudness of the two diaphragms independently of eachother, said -means permittmgeach diaphragm to be out out of operation.

48. A loudspeaker comprising a top memher and a base member arranged toform a housing open to the outer air, a cone diaphragm supportedhorizontally in-said housing, electromagnetic mechanism secured to 7 oneof said members for operatin said diaphragm, and manually adjusta 1emeans carried by said housing for re lating the operation of said diaragm rom outside the housing.

ADOLPH A. THOMAS.

